This application claims the priority benefit of Taiwan application Serial No. 89107669, filed Apr. 24, 2000.
1. Field of Invention
The present invention relates to a switch structure. More particularly, the present invention relates to an optical switch structure.
2. Description of Related Art
In opto-electronic communication, an optical switch that employs a micro-electromechanical system (MEMS) has become an important component for relaying optical signals. A conventional optical switch has a one-to-one crossbar configuration. FIG. 1 is a schematic layout of the mirrors inside a conventional one-to-one crossbar optical switch.
As shown in FIG. 1, the optical switch 10, such as 4-by-4 optical switch, consists of a set of 16 reflecting mirrors Sij arranged into a 4-by-4 matrix configuration where i and j are integers that range from 1 to 4 respectively. An incident beam enters the optical switch from the left in one of the four input optical paths I1, I2, I3 and I4. After an internal reflection takes place somewhere inside the optical switch, the incident beam leaves the optical switch 10 from the bottom out of one of the four output optical paths O1, O2, O3 and O4. All the reflecting mirrors Sij can be individually raised or lowered. If the reflecting mirror Sll is raised while all the other mirrors are lowered, the incident beam that enters the optical switch 10 through input optical path I1 will leave via output optical path O1. Similarly, the incident light beam from the optical path I1 can be redirected to output optical paths O2, O3 and O4 by raising the mirrors S12, S13 and S14 while lowering the other mirrors, respectively. To carry out optical switching, such as redirecting the incident beam from input optical path I3 to output optical path O4, the reflecting mirror S34 can be raised while all the other mirrors, including S31, S32, S33 and S44, are all lowered.
The raising and lowering of reflecting mirrors Sij is normally triggered by a control logic circuit (not shown in FIG. 1). By raising and lowering the reflecting mirrors in various combinations, the incident beam can be reflected by an internal mirror to any desired output optical path of the optical switch. Hence, switching multiple light sources to multiple destinations is possible. Each row and each column must have one reflecting mirror raised depending upon the incoming-to-outgoing light path. The raising and lowering of the reflecting mirrors within the optical switch is normally controlled by a hardware or software program. In general, the reflecting mirrors are moved and controlled by a micro-electromechanical system, existing in exsitent patents or papers.
The aforementioned crossbar arrangement of reflecting mirrors has one major drawback. As the switching optical paths increase, the number of reflecting mirrors inside the optical switch increases as the square of the number of input or output paths. However, putting too many reflecting mirrors inside an optical switch may lower production yield and reliability.
Aside from the one-to-one crossbar configuration, an optical switch that uses double-sided reflecting mirrors 24, 32, 34, 36 and 38 and fixed mirrors 22a, 22b is proposed in U.S. Pat. No. 4,815,827, which is shown in FIG. 2. Although multiple reflections are used to carry out the optical switching, the prior art structure still has to use many reflecting mirrors.
FIG. 2 is a schematic diagram showing an optical switch that utilizes multiple reflections. As shown in FIG. 2, the optical switch 20 includes two single-sided reflecting mirrors 22a and 22b. The reflecting mirrors 22a and 22b are parallel to each other with their reflecting surfaces facing each other. Symmetrically positioned between the two reflecting mirrors 22a and 22b is an axis Y. Along the axis Y are twelve double-sided equidistantly spaced reflecting mirrors 24. In addition, double-sided reflecting mirrors 32, 34, 36 and 38 are positioned between the reflecting mirrors 22a and 22b according to desired light-reflecting and switching conditions. With this structure, a 4-by-4 configuration switching can be achieved between input optical paths I1, I2, I3 and I4 and output optical paths O2, O3 and O4. However, the structure requires 16 double-sided mirrors altogether in addition to the two fixed mirrors 22a and 22b. Hence, other than equalizing the propagation distance in each of the optical routes, the number of reflecting mirrors is the same as the crossbar structure shown in FIG. 1, not reducing the number of the doubled-side reflecting mirrors.
In short, the one-by-one crossbar configuration inside the optical switch in FIG. 1 uses the largest number of reflecting mirrors. When a micro-electromechanical system is incorporated into the optical switch, the area needed to form the optical switch is proportional to the number of reflecting mirrors. In other words, the area required to form the optical switch is large when the one-by-one crossbar configuration is used. Hence, system production yield, system reliability and production cost all will be affected. If the number of reflecting mirrors inside the optical switch can be reduced without compromising its function, the manufacturing area can be reduced considerably. In addition, when the number of reflecting mirrors is reduced, circuits for driving the reflecting mirror are correspondingly reduced, and possible errors, chance of failures and power consumption of the optical switch are all lowered. Consequently, reducing the number of reflecting mirrors inside an optical switch not only improves the fabrication of internal optics, but also reduces complexity of control circuit elements as well.
Accordingly, one object of the present invention is to provide a multi-mirror reflection optical switch structure capable of reducing the number of reflecting mirrors used and hence the required area of the optical switch.
A second object of the invention is to provide a multi-mirror reflection optical switch structure capable of simplifying control circuitry inside the optical switch by reducing the number of reflecting mirrors.
A third object of the invention is to provide a multi-mirror reflection optical switch structure capable of reducing operational error, failure rate and power consumption because of reducing the number of reflecting mirrors.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a 4-by-4 optical switch structure. The optical switch includes a first and a second fixed reflecting mirror, a first double-sided reflecting mirror group that includes a first, a second and a third double-sided reflecting mirror and a second double-sided reflecting mirror group that includes a fourth, a fifth and a sixth double-sided reflecting mirror. The reflecting side of the first and the second fixed reflecting mirrors are facing each other. The two fixed mirrors are parallel to each other and symmetrically positioned about an axis of symmetry. The first, the second and the third double-sided reflecting mirrors are positioned at equal distances from each other along a symmetric axis between the first fixed reflecting mirror and the axis of symmetry. The fourth, the fifth and the sixth double-sided reflecting mirrors are positioned at equal distances from each other along a symmetric axis between the second fixed reflecting mirror and the axis of symmetry. The first and the fourth, the second and the fifth, the third and the sixth double-side reflecting mirrors are symmetrically positioned. Furthermore, the first, the second, the third, the fourth, the fifth and the sixth reflecting mirrors all are capable of being raised or lowered to carry out optical switching. By controlling the raising and lowering of the six movable double-sided reflecting mirrors, incoming light is permitted to reflect between the first and the second fixed reflecting mirrors. Optical switching is achieved by raising one or more of the six double-sided reflecting mirrors.
The invention also provides a second 4-by-4 optical switch structure. The optical switch includes a first and a second fixed reflecting mirror, a first double-sided reflecting mirror, a first double-sided reflecting mirror group that includes a second and a third double-sided reflecting mirror and a second double-sided reflecting mirror group that includes a fourth and a fifth double-sided reflecting mirror. The reflecting side of the first and the second fixed reflecting mirrors are facing each other. The two fixed mirrors are parallel to each other and symmetrically positioned about an axis of symmetry. The first double-sided mirror is parallel to and positioned on the axis of symmetry. The second double-sided reflecting mirror is positioned along a symmetrical axis between the first fixed reflecting mirror and the axis of symmetry. The third double-sided mirror is positioned along a symmetric axis between the second fixed reflecting mirror and the axis of symmetry. The centers of the first and the third double-sided reflecting mirrors and the second fixed reflecting mirror are aligned. Similarly, the centers of the first and the second double-sided reflecting mirrors and the first fixed reflecting mirror are aligned. The second double-sided reflecting mirror group is positioned next to the first double-sided reflecting mirror group. The fourth double-sided mirror is positioned along a symmetric axis between the first fixed reflecting mirror and the axis of symmetry. The fifth double-sided mirror is positioned along a symmetric axis between the second fixed reflecting mirror and the axis of symmetry. All five double-sided reflecting mirrors are capable of being raised or lowered to carry out optical switching. By controlling the raising and lowering of the five double-sided reflecting mirrors, incoming light is permitted to reflect between the first and the second fixed reflecting mirrors. Optical switching is achieved by raising one or more of the five double-sided reflecting mirrors.
The invention also provides a third 4-by-4 optical switch structure. The optical switch includes a first and a second fixed reflecting mirror, a first double-sided reflecting mirror group that includes a first and a second double-sided reflecting mirror, a second double-sided reflecting mirror group that includes a third and a fourth double-sided reflecting mirror and a fifth double-sided reflecting mirror. The reflecting side of the first and the second fixed reflecting mirrors are facing each other. The two fixed mirrors are parallel to each other and symmetrically positioned about an axis of symmetry. The first double-sided mirror is positioned along a symmetric axis between the first fixed reflecting mirror and the axis of symmetry. The second double-sided mirror is positioned along a symmetric axis between the second fixed reflecting mirror and the axis of symmetry. The second double-sided reflecting mirror group is positioned next to the first double-sided reflecting mirror group. The third double-sided mirror is positioned along a symmetric axis between the first fixed reflecting mirror and the axis of symmetry. The fourth double-sided mirror is positioned along a symmetric axis between the second fixed reflecting mirror and the axis of symmetry. The fifth double-sided reflecting mirror lies on the axis of symmetry close to the second double-sided reflecting mirror group. The fifth double-sided reflecting mirror is positioned about one mirror length distance away from the symmetrical point of the symmetric axis of the third and fourth double-sided reflecting mirrors. All five double-sided reflecting mirrors are capable of being raised or lowered to carry out optical switching. By controlling the raising and lowering of the five double-sided reflecting mirrors, incoming light is permitted to reflect between the first and the second fixed reflecting mirrors. Optical switching is achieved by raising one or more of the five double-sided reflecting mirrors.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.